Internal-ribbed exhaust nozzle for jet propulsion devices



Oct. 18, 1960 A. FERRI 2,956,400

INTERNAL-RIBBBD EXHAUST NOZZLE FOR JET PROPULSION mavzcas Filed June 5,1957 3 Sheets-Sheet 1 INVENTOR. ANTEINID FERRI AEENT Oct. 18, 1960 A.FERRI INTERNAL-RIBBED- EXHAUST NOZZLE FOR JET PROPULSION DEVICES FiledJune 5, 1957 3 Sheets-Sheet 2 INVENTOR. ANTDNID FEHRI AEENTINTERNAL-RIBBED EXHAUST NOZZLE FOR JET PROPULSION DEVICES AEIENTINTERNAL-RIBBED EXHAUST NOZZLE FOR JET PROPULSION DEVICES Antonio Ferri,Rockville Centre, N.Y., assignor to Curtiss-Wright Corporation, acorporation of Delaware Filed June 5, 1957, Ser. No. 663,671

7 Claims. (Cl. Gil-35.6)

My invention relates to an exhaust nozzle for jet propulsion devices.More particularly the invention is directed to an internal-ribbed nozzlehaving particular application to aircraft jet engines.

A prime object of the invention is to provide a suitable jet engineexhaust nozzle which may be constructed in a considerably shorter lengththan conventionally designed nozzles known in the art.

It is another object of the invention to provide such a nozzle which hasvariable area means for controlling the amount of expansion within thenozzle.

Other objects and advantages of the invention will become apparentduring a reading of the specification.

The nozzle of the invention includes a central three dimensional axiallysymmetric passage and a plurality of other passages, which arepreferably substantially two dimensional, surrounding the centralpassage. The passages located about the central passage are formed bythe side walls of a number of rib-like members. Although the centralpassage and surrounding passages are not physically separated by adividing wall, nevertheless, the respective passages are defined by thematching of longitudinal pressure gradients. By expanding a portion ofthe gas flow through the nozzle in the central passage and the remainingportion of the flow in the other passages, the length of the nozzle maybe considerably reduced over that required for a nozzle with the sameminimum area for the passage of gases having only the usual axiallysymmetric passage.

Referring to the drawings:

Fig. l is a longitudinal sectional view through the nozzle of theinvention.

Fig. 2 is a cross-sectional View taken on the plane of the line 2-2; ofFig. 1.

Fig. 3 is a cross-sectional view taken on the plane of the line 33 ofFig. 1.

Fig. 4 is a plan development of the inside of the nozzle showing thespoke-like members of the nozzle.

Fig. 5 is a longitudinal sectional view of a spoke-like nozzle providedwith closure flaps for varying the throat area of the nozzle.

Pig. 6 is a sectional view taken on the plane of the line 66 of Fig. 5.

Fig. 7 is a transverse sectional view taken on the plane of the line 7-7of Fig. 1.

Fig. 8 is a transverse sectional view taken on the plane of the line 8-%of Fig. 1.

Reference is made to Figures 1-4 inclusive of the drawings whereinreference character 1 designates a converging-diverging nozzle embodyingfeatures of the invention. Such nozzle has a three dimensional cen ralaxially symmetric passage 2 and a plurality of other longitudinallyextending passages 3 disposed about the central passage between rib-likemembers 4 projecting rom the nozzle wall 5. As shown, the centralpassage and surrounding passages are converging-diverging in form. Suchpassages extend throughout only a portion of the overall length of thenozzle. The lengths of the atent 2,955,400 Patented Oct. 18, 1960central and surrounding passages are determined by the lengths of therib-like members 4, and beyond the ends 6 of the rib-like members thecentral and surrounding passages merge. The rib-like members 4, andtherefore the separate passages, may in theory be extended to theextreme end 7 of the nozzle, however, because of very thin rib sectionswhich would be required at the exit, it is generally desirable toterminate the members 4 short of the end of the nozzle as shown.

With the desicribed construction, gas flow through the nozzle is in partexpanded in the central axially symmetrical passage 2, and in part inthe other passages 3 about the central passage. As shown the insidesurface 8 of the nozzle wall is parallel to the axially asymmetriccontour defined by the rib surfaces 8; and as a result the pasages 3 aresubstantially two dimensional and expansion in such passages take placecircumferentially. There are no physical boundaries between the centralpassages 2 and other passages 3. However, longitudinal pressuregradients between the central and other passages are substantiallymatched at least over most of the length of the rib members by properlydesigning the longitudinal extending passages 3 between the rib walls 9in a well known manner so that there is substantially no expansion ofthe gas flow in the central passage into the other passages.

The rib-like members 4 of the nozzle terminate a short distance upstreamfrom the throat 10 of the axially symmetric passage. The two dimensionalpassages have throats 11 located in the vicinity of the throat 10,however, the throats 11 do not necessarily occupy the same longitudinalposition in the nozzle as the throat 10. With an axially symmetricpassage of a minimum length type, that is, such as to provide a maximumthrust in the shortest possible length, the throats of the two dimensional passages are preferably disposed upstream from the throat 10 ofthe axially symmetric passage. This is because of an abrupt divergenceat the throat of an axially symmertic passage of the minimum length typeand a resulting pressure discontinuity. In order to match pressuresbetween the two dimensional passage and axially symmetric passage at thethroat of the axially symmetric passage it would be necessary to have adiscontinuity in area in each of the two dimensional passages. Suchdiscontinuity in area would cause =flow separation. It is thereforepreferable to fair the rib contour over the discontinuity therebyplacing the throat of the two dimensional passage 21 short distanceupstream from the throat of the axially symmetric passage.

Reference is now made to Figures 5 and 6 showing a rib-like nozzleprovided with structure for varying nozzle geometry. The effectivethroat area of such nozzle includes the throat area of the axiallysymmetric passage 12 and the throat area of the two dimensional passages13, formed by the ribs 14 extending from the nozzle wall 15. The throatarea of the passages 13 is, however, readily varied as by fiaps l6pivoted in the nozzle as at 17 at the upstream ends of the rib-likemembers 14, and operable between the ribs. The flaps 16 are operablebetween closed positions in which they obstruct the flow of gases intothe two dimensional passages such that the effective throat area of thenozzle is equal to the throat area of the axially symmetric passage 12,and open positions in which the flaps set in recesses 19 in the nozzlewall to provide a maximum efiective throat for the nozzle. The flaps maybe disposed between their open and closed positions to provide anyintermediate efiective throat size for the nozzle. Various positions ofthe flaps for controlling the effective throat area of the nozzle areshown in Figures 5 and 6. The flap positions may be adjusted in responseto control signals by any suitable mechanism which may, for example,include the hydraulically operated piston 20 in cylinder 21, a ring 22connected to the piston, and linkages 23, 24, and 25 connecting the ringto each of the flaps.

It will now be apparent that I have devised a nozzle of unique designwhich by permitting expansion through a central axially symmetricalpassage and surrounding twodimensional passages, provides for a nozzleof reduced length. Furthermore, as indicated the nozzle may be readilyadapted to vary its geometry, and so provide a nozzle which may beoperated efiiciently under various conditions. Because of the adjustablefeature the nozzle is of course particularly suitable for use on theafterburner of a gas turbine engine of a jet aircraft.

It should of course beunderstood that this invention is not limited tothe specific details of construction and arrangement thereof hereinshown and described, and that changes and modifications may occur to oneskilled in the 7 art without departing from the spirit of the invention.

I claim as my invention:

1. An exhaust nozzle for a jet engine comprising a nozzle wall having aplurality of rib-like members extending therefrom to define a centralaxially symmetric converging-diverging passage and a plurality ofperipheral converging-diverging passages about the central passagebetween the rib-like members communicating with said central passage,said peripheral passages being formed with throats disposed upstreamfrom the throat of the axially symmetric passage.

2. An exhaust nozzle for a jet engine comprising a nozzle Wall having aplurality of lib-like members extending therefrom to define a centralaxially symmetric converging-diverging passage and plurality ofperipheral converging-diverging passages about the central passagebetween the rib-like members and communicating with said centralpassage, the nozzle also having flaps movable in the peripheral passagesfor varying the nozzle throat area.

3. An exhaust nozzle for a jet engine comprising a nozzle wall having aplurality of rib-like members extending inwardly therefrom defining anozzle passage having a central converging-diverging portion and aplurality of peripheral converging-diverging port-ions extendingradially from said central portion and communicating therewith anddisposed between said rib-like members, said wall extending downstreambeyond said central and peripheral portions.

4. An exhaust nozzle as defined in claim 3 wherein said rib-like membersare aerodynamically contoured to provide said peripheral portionsadapted to substantially match pressures longitudinally at theboundaries of said central and peripheral portions.

5. An exhaust nozzle for a jet engine comprising a nozzle wall ofcircular cross-section having a plurality of longitudinally disposedrib-like members extending radially inward therefrom a distance lessthan the radius of said nozzle, said rib-like members having innerfacesdefining a central passage of first converging-diverging contour andlateral faces defining with said wall a plurality of peripheral passagesof second converging-diverging contour and communicating with saidcentral passage, said wall extending downstream beyond said central andperipheral passages.

6. An exhaust nozzle for a jet engine comprising a nozzle Wall ofcircular cross-section having a plurality of rib-like members extendingradially inward therefrom a distance less than the radius of saidnozzle, said rib-like members having inner faces contoured to define acentral converging-diverging passage having a throat, said rib-likemembers having lateral faces contoured to define a plurality ofperipheral converging-diverging passages having throats andcommunicating with said central passage, the throats of .said peripheralpassages being positioned upstream from said central throat.

7. An exhaust nozzle as defined in claim 6, wherein there are disposed aplurality of flaps between said rib-like members, said flaps havingtheir upstream ends pivotally mounted to thenozzle Wall adjacent to theupstream ends of said rib-like members and their downstream endsarcuately movable between said rib-like members to vary the throat areasof said peripheral passages, and means for imparting arcuate motion tosaid flaps.

References Cited in the file of this patent UNITED STATES PATENTS2,481,059 Africano Sept. 6, 1949 2,486,019 Goddard Oct. 25, 19492,579,043 Kallal Dec. 18, 1951 2,623,465 Jasse Dec. 30, 1952 2,625,008Crook Jan. 13, 1953 2,682,147 Ferris June 29, 1954 2,744,380 McMillan etal May 8, 1956 FOREIGN PATENTS 506,839 Italy Dec. 27, 1954

